A magnetic tape recording and/or reproducing mechanism is disclosed in U.S. Pat. No. 4,672,476, for example. The mechanism comprises one or more cam(s) which are driven by a motor and operating members which are operated by the cam(s), and the operating mode of the mechanism is changed to various modes, for example, EJECT, PLAY, FF/REW, REV, PAUSE, according to the relative positions of the operating members. Here, the motor is precisely controlled by a servo control circuit which is controlled in turn by a microprocessor.
The microprocessor receives both commands to make the mechanism's and peripheral circuits to be operated at the user's direction, and detected information for the mechanism state to protect the mechanism and the magnetic tape from an abnormal operation. Upon receipt of the user's command through keyboard or remote control input, the microprocessor provides a control signal to the servo control circuit of the drive motor for changing the state of the mechanism to execute the commanded mode. After changing the state of the mechanism to the commanded operating mode, the microprocessor completes the output of a control signal upon receipt of detected information from the detecting means for the state of the mechanism.
Therefore, with the above mentioned U.S. Pat. No. 4,672,476 magnetic tape recording and/or reproducing apparatus or drive mechanism to execute multiple modes, a detecting stage for the state of the mechanism is generally provided.
As the detecting means, a programmable switch having multiple contacts or a plurality of a switches having a single contact has been generally used. Such a programmable switch may be a conventional slide or rotary type switch.
In FIG. 1 and FIG. 2, a conventional slide type programmable switch and timing charts of its switching signals are illustrated. The programmable switch consists of a base plate 1 in which a plurality of contact bands 1a, 1b, 1c, 1d are arranged in parallel; a contact 2 having a plurality of contact wiper portions 2a, 2b, 2c, 2d each of which corresponds to the contact bands 1a, 1b, 1c, 1d, respectively; and a slider 3 for moving the contactor 2. The slider 3 is further connected to the actuator 4 which reciprocates along the predetermined stroke according to changes of the operating mode by a drive mechanism (not shown). When the slider 4 is displaced by the actuator 4, the contactor 2 connected thereto is displaced together, thereby making electrical contacts between the contacting bands 1a, 1b, 1c, 1d and the contacting portions 2a, 2b, 2c, 2d, respectively.
Here, three contacting bands 1b, 1c, 1d excluding the single contacting band 1a for grounding are formed in a predetermined pattern so that only the hatched portions make contact with the contacting portions 2b, 2c, 2d. Therefore, switching pulses or signals of high or low level are generated at the contacting bands 1b, 1c, 1d excluding band 1a according to the position of the contactor 2, and the detected signals for determining the status of the mechanism to execute specific operating modes are output by combining the switching pulses.
In the above mentioned conventional programmable switch, the contacting force between each of the contact elements should be maintained in an adequate range to generate proper detected signals, but a loose contact may occur by wear and tear as with time passing-by, thereby causing an erroneous operation of the mechanism.